The present invention relates to a steering column assembly for a vehicle, and more specifically to a steering column assembly including a mounting bracket designed to absorb impact energy in a secondary collision.
In a secondary collision of the driver against the steering wheel, a load is applied on the steering column in the axial direction. In a bending type impact absorbing structure, a mounting bracket is bent forwards toward the front of the vehicle by this axial load.
FIGS. 5.about.7 show one conventional bending type impact absorbing steering column assembly. A mounting bracket 1 has left and right horizontal upper walls 2 to be fixed to the vehicle body, left and right bent portions 3, left and right vertical front walls 4 and left and right vertical side walls 5 formed with elongate holes 9. An approximately U-shaped column support member (or distance bracket) 7 is clamped between the left and right side walls 5 of the mounting bracket 1. A steering column 8 is fixedly supported on the column support member 7.
A clamping bolt 10 passes through the elongate holes 9 of the mounting bracket and holes of the column support member 7. A nut 16 fixed to a tilt lever 13 is screwed on a threaded end of the clamping bolt 10.
The steering column assembly of FIGS. 5, 6 and 7 further includes rotation preventing member 11 and sliding contact plate 12 both mounted on the clamping bolt 10 on opposite sides of the mounting bracket 1. The rotation preventing member 11 is received and engaged in the elongate hole 9 on the right side as viewed in FIG. 7. The rotation preventing member 11 is movable up and down in the right side elongate hole 9. The sliding contact plate 12 is received and engaged in the elongate hole 9 on the left side, and mounted on the clamping bolt 10 between the nut 16 of the tilt lever 13 and the side wall 5 on the left side. The sliding contact plate 12 has a projection 15 for limiting a rotational movement of the tilt lever 13. The sliding contact plate 12 has side surfaces producing frictional forces with the side wall 5 of the mounting bracket 1 and the nut 16, and improves the holding or fastening force with the frictional forces.
In the state in which an arm of the tilt lever 13 is pulled up to an uppermost position, and a projection 14 of the tilt lever 13 abuts on the projection 15 of the sliding contact plate 12, the nut 16 integral with the tilt lever 13 is tightened on the clamping bolt 10, the column support member 7 is clamped between the left and right side walls 5 of the mounting bracket 1, and this steering column assembly firmly holds the steering column 8 at a desired position with the frictional forces. By rotating the arm of the tilt lever 13, the driver can remove the clamping force of the clamping bolt 10, and adjust the steering column 8 up and down along the elongate holes 9 of the mounting bracket 1.
The tilt lever 13 is normally kept unobstructive above the knees of the driver. In a head-on collision of the vehicle, the driver collides against the steering wheel, and a force F is applied on the steering column 8 in the axial direction. By this force, the steering column 8 is shoved forwards along the axial direction, and the mounting bracket 1 is deformed so that the front walls 4 swing forward about the bent portions 3, and the angle between the front walls 4 and the upper wall 2 becomes greater. With this deformation, the clamping bolt 10 moves together with the side walls 5 through the stopper 11 engaging with the right side elongate hole 9. At the same time, the projection 15 of the plate 12 in engagement with the left side elongate hole 9 pushes the tilt lever 13, and the tilt lever 13 is rotated downward as shown by an arrow R in FIG. 8 to a lower position shown by two dot chain lines. At the lower position, the tilt lever 13 projects toward the driver's knees.